Coupling the colliding continents doesn't work for me?

Hello. I am using Artifexian’s tutorial (relatively, at least - since I don’t put much detail into the ocean crust I form every timestep), and have recently collided two continents - let’s call them A (ID:100) and I (ID:900).
image

This is the .rot file. As per the tutorial, I input the coordinates of the child plate ID when the anchored plate ID is the parent one (e.g. 100). Now that I’ve input the correct coordinates this morning, one of the “bugs” where the continent I just got back where it separated from the initial continent it was a part of before being rifted apart, is no longer the viable (e.i. it got resolved). However, when I still want to move continent A, it doesn’t highlight continent I as well, leading me to believe I’ve done something wrong in the .rot file. How do I fix this? Help much appreciated!

P.S. Don’t pay attention to the oceanic crust and the flowlines - I haven’t sorted them out yet in this timestep, as I haven’t even really moved all of the continents yet.